It is already known that due to statutory regulations motor vehicles, which are in particular equipped with a diesel- or petrol engine, can continue to be operated in a protected operating mode, i.e. with the aid of a limp-home function, if a fault symptom has been diagnosed in the engine or one of the vehicle units.
It is further known that the limp-home function is implemented as a rule in an engine control unit, which is geared in particular to the tasks of optimum engine control with regard to a maximum torque, minimal exhaust gas emissions and optimum driving comfort. It is however a drawback that, if a fault symptom is detected, for example if a boost pressure sensor of a turbocharged engine is defective and this may lead to serious damage of a relevant component, in this case the exhaust-gas turbocharger, there is no limp-home reaction that is dependent upon the driving state. The result of this is in practice that because of the limitation of the torque the vehicle is no longer capable of greater acceleration, which may be necessary particularly in a critical driving situation. The lack of acceleration of the motor vehicle may therefore lead to endangerment of the driver and the vehicle if the driver as a result of the limitation of the torque is suddenly no longer able to adapt the control of his motor vehicle to the actual traffic situation.